1. Field of the Invention
The invention relates to a subassembly which is used in the production of an aquatic gliding board, especially a surfboard.
The invention also relates to a method for manufacturing such a subassembly and to a board manufactured using the subassembly.
2. Description of Background and Relevant Information
Conventionally, a surfboard is made from a foam blank, especially polyurethane foam blank, that is made in a mold. The foam blank is machined by planing and sanding over a small thickness to locally customize its shape, then it is covered with a casing made of resin-impregnated glass fibers that forms a reinforcing outer shell and provides the board with its final shape. A decoration and a glassing provide the board with its final appearance.
In certain cases, the foam blank is cut longitudinally into two portions that are then glued to a wooden stringer that reinforces its structure and imparts a predetermined longitudinal camber thereon.
The disadvantage of such a construction technique is the weight of the final board. Indeed, the foam is relatively thick; typically, its density is about 50 kg/m3. In addition, it is a priori not possible to reduce the density of the foam without negatively affecting the mechanical properties of the board.
According to another construction technique derived from the sailboard, one begins with a relatively low density foam blank that is machined to shape. This blank is covered with a layer of resin-impregnated glass fibers. A casing made of a higher density foam is attached around this subassembly. Layers of resin-impregnated glass fibers are then applied in order to form the outer shell.
Such a construction mode enables a savings in weight of about 20% or more while maintaining a good rigidity beneath the feet. However, its implementation is relatively complex. Moreover, the central foam blank is generally made of polystyrene foam. This material has the flaw of taking in water. Over the course of its lifetime, the board sometimes hits a reef or a rock. If the outer shell is damaged, there is a risk of water penetration, the water weighing down the board and being particularly difficult to evacuate.
Finally, it is known to make hollow boards with sandwich layers. Alternatively, two half-shells are made and then assembled to one another, or yet the assembly is made in a closed mold with an inner bladder that is inflated to push and press the sandwich layers against the walls of the mold.
This manufacturing technique makes it possible to make lightweight boards. However, it is not possible to customize the shape of the board. In this case, the shape of the outer shell depends exclusively upon the shape of the mold.
An object of the invention is to propose an improved subassembly, which makes it possible to make surfboards that are lighter while preserving a shape that can be customized, or more voluminous for an equal weight.
This object is achieved by a structural subassembly which, according to the invention, includes a hollow inner shell covered with a casing made of foam capable of being machined.
The board is characterized in that it includes the predefined assembly coated with at least one layer of resin-impregnated fibers.